Process for the preparation of protected L-alanine derivatives

Abstract

The present invention is directed to a novel process for the preparation of protected L-alanine derivatives, useful as intermediates in the synthesis of compounds useful as mu / delta opioid modulators.

Description

CROSS REFERENCE TO RELATED U.S. APPLICATION DATA

[0001] The present application is derived from and claims priority to provisional application U.S. Ser. No. 61 / 108,649, filed Oct. 27, 2008, which is herein incorporated by reference in its entirety.FIELD OF THE INVENTION

[0002] The present invention is directed to a novel process for the preparation of protected L-alanine derivatives, useful as intermediates in the synthesis of compounds useful as mu / delta opioid modulators.BACKGROUND OF THE INVENTION

[0003] The opioid receptors were identified in the mid-1970's, and were quickly categorized into three sub-sets of receptors (mu, delta and kappa). More recently the original three types of receptors have been further divided into sub-types. Also known is that the family of opioid receptors are members of the G-protein coupled receptor (GPCR) super-family. More physiologically pertinent are the well established facts that opioid receptors are found throughout the central and peripheral nervou...

Examples

example 1

Preparation of 2-tert-Butoxycarbonylamino-3-(4-carbamoyl-2,6-dimethyl-phenyl)-propionic acid methyl ester

[0108]

STEP A

[0109]Dry DMAc (300 mL), 2-Me-THF (150 mL), I2 (25.4 g, 0.10 mol) and zinc powder (294.3 g, 4.5 mol), were added under nitrogen to a 3 L four-necked round bottom flask equipped with an addition funnel, mechanical stirrer, heating mantel, condenser and thermocouple. The resulting slurry was stirred until the red color of I2 disappeared (about 2 minutes). During the addition, a temperature increase was observed (from 23° C. to 43° C.). The resulting mixture was cooled down using an ice / NaCl bath to about −5° C. to −2° C. While at this temperature, a solution of Boc-6-iodo-alanine-OCH3 (also known as 2-tert-butoxycarbonylamino-3-iodo-propionic acid methyl ester, 658.3 g, 2.0 mol) in a mixture of DMAc (250 mL) and 2-Me-THF (500 mL) was added slowly over a period of 2 hours. The temperature of the resulting mixture was maintained below 10° C. and the mixture aged for a per...

example 2

Preparation of (S)-2-tert-Butoxycarbonylamino-3-(4-cyano-2,6-dimethyl-phenyl)-propionic acid methyl ester

[0112]

[0113]A 50 mL three-necked round bottom flask equipped with an addition funnel, magnetic stirrer, heating mantel, and thermocouple was charged under nitrogen dry DMAc (2 mL), I2 (38.1 mg, 0.15 mmol) and zinc powder activated (washed with 10% HCl, rinsed with H2O and acetone) (393 mg, 6 mmol). The resulting mixture was stirred at 23° C. until the red color of I2 disappeared (2 minutes). A solution of Boc-β-iodo-L-alanine methyl ester (1 g, 3 mmol) in DMAc (2 mL) was added slowly, (temperature change from 21° C. to 29° C.) and the resulting mixture was stirred at 80° C. for 0.5-1 hour, then co cooled to 35° C. To the resulting mixture were added, successively, 4-bromo-3,5-dimethyl-benzonitrile (315 mg, 1.5 mmol) in DMAc (6 mL), P(o-tol)3 (36.5 mg, 0.12 mmol) and Pd2(dba)3 (55 mg, 0.06 mmol). The resulting mixture was heated to 70° C., with stirring for 1 hour, then cooled to ...

example 3

Preparation of (S)-2-tert-Butoxycarbonylamino-3-(4-cyano-2,6-dimethyl-phenyl)-propionic acid methyl ester

[0114]

STEP A: Boc-β-iodo-Alanine methyl ester

[0115]A 2 L four-necked round-bottomed flask equipped with a nitrogen inlet, a mechanical stirrer, an addition funnel and a thermocouple was charged with anhydrous DMAc (500 mL) and iodine (16.8 g, 0.06 mol) to yield a red solution. To the stirred solution was then added zinc powder (143.9 g, 2.2 mol). The red color of the resulting mixture was observed to disappear in about 2 minutes, and an exotherm (22° C. to about 36° C.) was observed. The resulting mixture was cooled to −8° C. and then a solution of N-(tert-butoxycarbonyl)-3-iodo-L-alanine methyl ester (658 g, 2.0 mol) in anhydrous DMAc (500 mL) was added slowly over about 2 hours, maintaining the mixture temperature at below about 10° C., without stirring. The resulting cooled mixture was used in the next step without further manipulation.

STEP B: (S)-2-tert-Butoxycarbonylamino-3-...

CROSS REFERENCE TO RELATED U.S. APPLICATION DATA

[0001] The present application is derived from and claims priority to provisional application U.S. Ser. No. 61 / 108,649, filed Oct. 27, 2008, which is herein incorporated by reference in its entirety.FIELD OF THE INVENTION

[0002] The present invention is directed to a novel process for the preparation of protected L-alanine derivatives, useful as intermediates in the synthesis of compounds useful as mu / delta opioid modulators.BACKGROUND OF THE INVENTION

[0003] The opioid receptors were identified in the mid-1970's, and were quickly categorized into three sub-sets of receptors (mu, delta and kappa). More recently the original three types of receptors have been further divided into sub-types. Also known is that the family of opioid receptors are members of the G-protein coupled receptor (GPCR) super-family. More physiologically pertinent are the well established facts that opioid receptors are found throughout the central and peripheral nervou...

Examples

example 1

Preparation of 2-tert-Butoxycarbonylamino-3-(4-carbamoyl-2,6-dimethyl-phenyl)-propionic acid methyl ester

[0108]

STEP A

[0109]Dry DMAc (300 mL), 2-Me-THF (150 mL), I2 (25.4 g, 0.10 mol) and zinc powder (294.3 g, 4.5 mol), were added under nitrogen to a 3 L four-necked round bottom flask equipped with an addition funnel, mechanical stirrer, heating mantel, condenser and thermocouple. The resulting slurry was stirred until the red color of I2 disappeared (about 2 minutes). During the addition, a temperature increase was observed (from 23° C. to 43° C.). The resulting mixture was cooled down using an ice / NaCl bath to about −5° C. to −2° C. While at this temperature, a solution of Boc-6-iodo-alanine-OCH3 (also known as 2-tert-butoxycarbonylamino-3-iodo-propionic acid methyl ester, 658.3 g, 2.0 mol) in a mixture of DMAc (250 mL) and 2-Me-THF (500 mL) was added slowly over a period of 2 hours. The temperature of the resulting mixture was maintained below 10° C. and the mixture aged for a per...

example 2

Preparation of (S)-2-tert-Butoxycarbonylamino-3-(4-cyano-2,6-dimethyl-phenyl)-propionic acid methyl ester

[0112]

[0113]A 50 mL three-necked round bottom flask equipped with an addition funnel, magnetic stirrer, heating mantel, and thermocouple was charged under nitrogen dry DMAc (2 mL), I2 (38.1 mg, 0.15 mmol) and zinc powder activated (washed with 10% HCl, rinsed with H2O and acetone) (393 mg, 6 mmol). The resulting mixture was stirred at 23° C. until the red color of I2 disappeared (2 minutes). A solution of Boc-β-iodo-L-alanine methyl ester (1 g, 3 mmol) in DMAc (2 mL) was added slowly, (temperature change from 21° C. to 29° C.) and the resulting mixture was stirred at 80° C. for 0.5-1 hour, then co cooled to 35° C. To the resulting mixture were added, successively, 4-bromo-3,5-dimethyl-benzonitrile (315 mg, 1.5 mmol) in DMAc (6 mL), P(o-tol)3 (36.5 mg, 0.12 mmol) and Pd2(dba)3 (55 mg, 0.06 mmol). The resulting mixture was heated to 70° C., with stirring for 1 hour, then cooled to ...

example 3

Preparation of (S)-2-tert-Butoxycarbonylamino-3-(4-cyano-2,6-dimethyl-phenyl)-propionic acid methyl ester

[0114]

STEP A: Boc-β-iodo-Alanine methyl ester

[0115]A 2 L four-necked round-bottomed flask equipped with a nitrogen inlet, a mechanical stirrer, an addition funnel and a thermocouple was charged with anhydrous DMAc (500 mL) and iodine (16.8 g, 0.06 mol) to yield a red solution. To the stirred solution was then added zinc powder (143.9 g, 2.2 mol). The red color of the resulting mixture was observed to disappear in about 2 minutes, and an exotherm (22° C. to about 36° C.) was observed. The resulting mixture was cooled to −8° C. and then a solution of N-(tert-butoxycarbonyl)-3-iodo-L-alanine methyl ester (658 g, 2.0 mol) in anhydrous DMAc (500 mL) was added slowly over about 2 hours, maintaining the mixture temperature at below about 10° C., without stirring. The resulting cooled mixture was used in the next step without further manipulation.

STEP B: (S)-2-tert-Butoxycarbonylamino-3-...

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